M. Hyla, J. Filipecki, Z. Mandecki, R. Mervinskii.
Journal of Non-Crystalline Solids, vol. 232-234, 1998, p. 446-452.
Positron annihilation lifetime and X-ray diffraction measurements were made on photopolymers based on acrylate oligomers. Polymerization was caused by exposure to ultra violet light. The measurements were made on photopolymer specimens with different ultra violet light exposure times. The longest positron lifetime, t3, was associated with the pickoff annihilation of orthopositronium (o-Ps) trapped in voids. Interatomic distances and coordination numbers for the investigated samples have been determined from X-ray data. Ultra violet light exposure time affects mainly the sizes of the voids. The nearest neighbour distances and coordination numbers are independent of the ultra violet exposure time.